Device and method for protecting an optical observation opening

ABSTRACT

The invention relates to a diaphragm device ( 38 ) and to a method for protecting an optical observation opening ( 39 ), in particular for protecting the observation opening against contaminants from a dirty atmosphere ( 35 ) in a blast furnace or the like, having a nozzle unit and a purging gas chamber ( 43 ), wherein the nozzle unit forms a diaphragm aperture ( 26 ) for the observation opening and is used to form a purging gas flow, wherein the purging gas chamber is formed between an optical surface ( 41 ) of the observation opening and the diaphragm aperture. A purging gas is applied to the purging gas chamber and purging gas can be led through the diaphragm aperture into the dirty atmosphere, wherein the nozzle unit has a flow guiding device ( 31, 49 ) which effects guidance of the flow of purging gas escaping into the dirty atmosphere.

The invention relates to a diaphragm device and a method for protecting an optical observation opening, in particular for protecting the observation opening against contaminants from a dirty atmosphere in a blast furnace and the like, having a nozzle unit and a purging gas chamber, wherein the nozzle unit forms a diaphragm aperture for the observation opening and is used for forming a purging gas flow, wherein the purging gas chamber is formed between an optical surface of the observation opening and the diaphragm aperture, and wherein a purging gas is applied to the purging gas chamber and the purging gas can be ducted through the diaphragm aperture into the dirty atmosphere.

For observing an inner chamber of a blast furnace, it is known, for example, to provide observation openings, which allow a look into the blast furnace. Also, such an observation opening can be provided with a camera, which continuously films the inner chamber of a blast furnace for transmission to and display in a control room. The camera or also the observation opening itself can have a wide angle aperture, which allows for a comprehensive view into the inner chamber. Thus, a diaphragm aperture as small as possible of the observation opening can be realized with a conic aperture angle which substantially corresponds to an aperture angle of a wide angle lens. Also, in the observation opening, an optical protective screen is arranged, which has the purpose of protecting a wide angle lens or an observer against adverse heat radiation or dirt particles. Since there is an immense amount of dirt in a blast furnace atmosphere, the protective screen or the observation opening, respectively, would become dirty relatively fast and turn opaque. To avoid this, it is a known method to apply a purging gas flow to the protective screen, for example of nitrogen, in such a manner that purging gas is guided past the protective screen and escapes through the diaphragm aperture into the dirty atmosphere of the blast furnace. In doing so, dirt particles are prevented from reaching the protective screen.

Since the purging gas is blown at high pressure out of the diaphragm aperture into the dirty atmosphere, flows are created transverse to a purging gas flow which transport dirt particles in the direction of the diaphragm aperture. This results in dirt particles being increasingly deposited around the diaphragm aperture, on a frontal wall of the diaphragm aperture or of the blast furnace, causing the diaphragm aperture to be gradually covered by dirt moving in from a lateral edge. In particular if the diaphragm aperture is formed with an aperture angle, the purging gas escaping at high pressure cannot expand quickly enough, generating a negative pressure at a flank of the diaphragm aperture which causes vortices and increasingly draws in dirt particles, which accumulate, for example, in a cone of the diaphragm aperture and, thus, can reduce a field of vision of a lens. In conclusion, all these effects necessitate frequent cleaning of the diaphragm aperture. Also, this problem does not only occur in blast furnaces, but generally in all closed spaces with a dirty atmosphere which can dirty a diaphragm aperture of this kind.

It is therefore the object of the present invention to provide a diaphragm aperture and a method for protecting an optical observation opening which respectively prevent the fast dirtying of a diaphragm aperture.

This object is solved by a diaphragm device with the features of claim 1 and a method with the features of claim 17.

The diaphragm device according to the invention for protecting an optical observation opening, in particular for protecting the observation opening against contaminants from a dirty atmosphere in a blast surface or the like, comprises a nozzle unit and a purging gas chamber, wherein the nozzle unit forms a diaphragm aperture for the observation opening and serves for forming a purging gas flow, wherein the purging gas chamber is formed between an optical surface of the observation opening and the diaphragm aperture, wherein a purging gas is applied to the purging gas chamber and the purging gas can be guided through the diaphragm aperture into the dirty atmosphere, wherein the nozzle unit comprises a flow guiding device which effects or can effect a guiding of the flow of purging gas escaping into the dirty atmosphere.

In particular with the help of the flow guiding device it becomes possible to form a purging gas flow in such a manner that no negative pressure is formed on a flank of the diaphragm aperture due to the purging gas flow and thus a sucking in of dirt particles is avoided. Further, the purging gas flow is particularly pronounced in the area of an outer diameter of the diaphragm aperture so that a gradual covering of the diaphragm aperture by a frontal deposition of dirt particles is prevented. In contrast to the state of the art, in which a purging gas flow is created substantially based on the shape of the diaphragm aperture alone, in the invention, the formation of a targeted purging gas flow is possible, which prevents a deposition of dirt particles on the diaphragm aperture to the largest possible extent. For this purpose, a flow guiding device is formed in the nozzle unit, which can form a purging gas flow of this kind in the area of the diaphragm aperture. The optical surface can be realized as a simple plane-parallel plate or screen behind which an objective lens is arranged. Also, the optical surface can be formed by a lens of the objective lens itself. In this case, for example, a camera can also be arranged within the purging gas chamber.

In an advantageous embodiment, the purging gas chamber can be formed conic, tapering in the opening direction of the diaphragm aperture. This means, the purging gas chamber can already effect the formation of a purging gas flow which flows in particular along a flank of the diaphragm aperture at relatively high pressure. Also, the conic shape of the purging gas chamber can promote a laminar flow within the purging gas chamber and prevent the formation of vortices.

Further, the diaphragm aperture can be formed conic, widening in the opening direction of the diaphragm aperture. A conic diaphragm aperture is particularly advantageous if a wide angle lens is used for observation. An aperture angle of the diaphragm aperture can then substantially correspond to an aperture angle of the lens. Apart from that, the diaphragm aperture can also be formed slit-shaped, cylindrical or with straight flanks.

It is also advantageous if in the diaphragm aperture a circular annular duct is formed, by means of which purging gas can be supplied to the nozzle unit. In this way, the diaphragm aperture can be supplied with purging gas from all sides and a purging gas can be applied to the optical surface of the observation opening and/or a protective screen from all sides. Also in this way, pressure differences within the nozzle unit, which can lead to undesired turbulences of purging gas, can be prevented to the largest possible extent.

In this context, an annular duct can be formed such that a rotating flow of purging gas in the annular duct can be effected. A rotating flow can, for example, be caused by an eccentric, tangential introduction of purging gas into the annular duct or by lamellas influencing a flow direction.

An annular guiding of the purging gas flow as soon as in the annular duct can influence the purging gas flow leaving the diaphragm aperture in such a manner, that it leaves the diaphragm aperture with a twist, that is helically, which facilitates maintaining the cleanliness of the diaphragm aperture.

To avoid turbulences and vortices within the diaphragm aperture, it is advantageous if the flow guiding device is formed rotationally symmetric relative to a longitudinal axis of the diaphragm aperture. In an advantageous embodiment, the nozzle unit can comprise an internal flow guiding device which is formed in such a manner that a helical motion of the purging gas around a longitudinal axis of the diaphragm aperture can be effected. In particular in conic diaphragm apertures, a formation of a negative pressure in the area of flanks and, thus, a deposition of dirt particles can be avoided in this way. Due to thus generated centrifugal forces, the purging gas escaping helically or twisted expands relatively fast in a lateral direction transverse to the longitudinal axis of the diaphragm aperture so that the purging gas flow also touches the flank of the conic diaphragm aperture.

For forming this helical motion, the flow guiding device can be arranged between an annular duct and the purging gas chamber. In this way, the purging gas can flow into the purging gas chamber from all sides, wherein by means of the flow guiding device the purging gas undergoes an alteration of its flow direction and performs a circular or rotating motion in the purging gas chamber.

The internal flow guiding device can also be arranged between an annular duct and the diaphragm aperture. In this way, a rotation of the purging gas flow can then also be formed only in the area of the diaphragm aperture. This can be advantageous if a rotation of the purging gas flow within the purging gas chamber is undesirable.

Alternatively, the internal flow guiding device can be arranged between an annular duct and a transition area of the purging gas chamber and the diaphragm aperture. Said transition area can, for example, be a bottle-neck between the purging gas chamber and the diaphragm aperture, within which the internal flow guiding device is arranged.

The flow guiding device can be formed by flow ducts whose longitudinal duct axes run transverse relative to the longitudinal axis of the diaphragm aperture, respectively, without intersecting the longitudinal axis. This means, the flow ducts can be oriented relative to the longitudinal axis in such a manner that they enter the purging gas chamber tangentially, for example, so that a rotating purging gas flow is created in the purging gas chamber. It is advantageous as well if the flow ducts are oriented such that purging gas is directly applied to the optical surface so as to effectively preclude a deposition of dirt particles thereon.

Said flow ducts can be formed of drill holes or lamellas. This means, the flow guiding device can be formed of one or also of several drill holes which eccentrically lead into the purging gas chamber or the diaphragm aperture or into the transition area in a radial direction. The same effect of a rotating flow can be reached using lamellas. In that case, an even further-reaching influence on a purging gas flow is possible because the lamellas or their effective surface can also be inclined relative to a plane formed by the optical surface.

In a further advantageous embodiment, the nozzle unit can comprise an external flow guiding device, which at least forms an annular gap which surrounds the diaphragm aperture and from which purging gas can escape in an annular shape. Accordingly, a purging gas flow escaping through the diaphragm aperture is supplemented by a further purging gas flow, which coaxially surrounds it. This outer purging gas flow has the effect that contaminants depositing on the diaphragm aperture cannot advance into the diaphragm aperture because they cannot pass the annular gap due to the purging gas flow escaping from said gap. Also, a sucking in of dirt particles due to a partial negative pressure in the area of the diaphragm aperture is precluded because the purging gas escaping from the annular gap prevents such an intrusion of dirt particles into the diaphragm aperture as well.

The annular gap can be produced particularly easy if the annular gap is formed between an inner and an outer diaphragm ring of the nozzle unit. The nozzle unit can, for example, be formed of two or more diaphragm rings, wherein the outer diaphragm ring has an inner diameter into which the inner diaphragm ring can be inserted at least in portions so that an annular gap is created. For example, the diaphragm rings can be spaced from one another in a vertical direction relative to the longitudinal axis of the diaphragm aperture in such a way that an intermediate space or also an annular duct is formed, through which purging gas can flow into the annular gap. A flow guiding device can be produced particularly easy in this manner.

Consequently, the annular gap can be directly connected to an annular duct. If a rotating purging gas flow is already formed in the annular duct, a rotating motion of the purging gas flow can propagate past the annular gap into the dirty atmosphere and prevent an intrusion of dirt particles into the diaphragm aperture even more effectively due to the thus generated centrifugal forces of the purging gas flow.

Also, the annular gap can be formed conic, tapering in the opening direction of the diaphragm aperture. Due to this kind of conic realization of the purging gas flow leaving the annular gap, it becomes possible to concentrate the purging gas flow escaping from the diaphragm aperture so that turbulences, which are caused when the purging gas flow enters the dirty atmosphere, are displaced to a relatively large distance from the diaphragm aperture. By such an influencing or different realization of an exit angle of the purging gas flow from the annular gap, the position, shape and dimension of the vortices in the dirty atmosphere can be influenced. Also, an approach of dirt particles to the diaphragm aperture can be reduced.

To achieve a high exit speed of the purging gas from the annular gap, a gap duct of the annular gap can be formed such that it tapers in the opening direction of the diaphragm aperture.

A particularly good protective effect for the diaphragm aperture can be achieved if the annular gap is arranged directly on an outer diameter of the diaphragm aperture. Accordingly, the annular gap can be located directly in a transition area between an outer edge of the diaphragm aperture or of a flank and a front side adjacent thereto of a diaphragm ring or a chamber wall. However, other positions for forming the annular gap within the flank or at a distance from the diaphragm aperture on the front side are conceivable as well.

The method according to the invention for protecting an optical observation opening, in particular for protecting the observation opening against contaminants from a dirty atmosphere in a blast furnace or the like, is implemented using a nozzle unit and a purging gas chamber, wherein the nozzle unit forms a diaphragm aperture for the observation opening and serves for forming a purging gas flow, wherein the purging gas chamber is formed between an optical surface of the observation opening and the diaphragm aperture, wherein a purging gas is applied to the purging gas chamber and the purging gas is guided through the diaphragm aperture into the dirty atmosphere, wherein the nozzle unit comprises a flow guiding device by means of which a guiding of the flow of purging gas escaping into the dirty atmosphere takes place.

With respect to the advantages resulting from this method, reference is made to the description above. Further advantageous embodiments of the method result from the feature descriptions in the dependent claims referencing back to the device claim.

In the following, the invention is explained in more detail with reference to the enclosed drawings.

FIG. 1 shows a perspective sectional view of a blast furnace;

FIG. 2 shows a longitudinal sectional view of a diaphragm aperture according to the state of the art;

FIG. 3 shows a longitudinal sectional view of a diaphragm aperture with an embodiment of a flow guiding device;

FIG. 4 shows a longitudinal sectional view of a diaphragm device;

FIG. 5 shows a cross-sectional view of the diaphragm device of FIG. 4;

FIG. 6 shows a perspective sectional view of the diaphragm device;

FIG. 7 shows a further perspective sectional view of the diaphragm device;

FIG. 8 shows a perspective view of a nozzle unit;

FIG. 9 shows a top view of the nozzle unit;

FIG. 10 shows a longitudinal sectional view of the nozzle unit;

FIG. 11 shows a top view of a further nozzle unit;

FIG. 12 shows a longitudinal sectional view of a further nozzle unit.

FIG. 1 shows a blast furnace 10 with an inner chamber 11, a burden 12 and a dirty atmosphere 13 located above the burden 12 in the inner chamber 11. On an outer wall 14 of the blast furnace 10, a camera 15 is arranged on an observation opening with a diaphragm device, both not being illustrated. The camera 15 comprises a wide angle lens—not visible either—with which a picture of the inner chamber 11 can be filmed, said picture being located in a field of vision 16 or an aperture angle of the wide angle lens.

FIG. 2 shows a diaphragm aperture 17 according to the state of the art with a conic flank 19 formed relative to a longitudinal axis 18. A purging gas flow 20 is indicated here with arrows. Since the purging gas flow 20 leaves the diaphragm aperture 17 at high pressure and, thus, an expansion of the purging gas in a dirty atmosphere 21 cannot take place completely in the diaphragm aperture 17, a negative pressure forms in an area 22 of the flank 19, which generates a flow 23, indicated with arrows, in the dirty atmosphere 21. Dirt particles not illustrated here are carried along by the flow 23 from the dirty atmosphere 21 along a front side 24 of a diaphragm ring 25 into the diaphragm aperture 17 and, as illustrated, swirled in the area 22 or carried away by the purging gas flow 20. In this process, a deposition of dirt particles on the flank 19 and on the front side 24 in the proximity of the area 22 takes place. Here, so many dirt particles can accumulate, that the diaphragm aperture 17 is gradually covered and an aperture angle is reduced.

FIG. 3 shows a diaphragm opening 26, which is formed conic and rotationally symmetric to a longitudinal axis 27 and has an aperture angle α. In this case, the aperture angle α corresponds to an aperture angle of a wide angle lens not illustrated here on an observation opening. The diaphragm opening 26 thus forms a flank 28, which ends in an outer diameter d on a front side 29 of an outer diaphragm ring 30. In the outer diaphragm ring 30, an external flow guiding device 31 is further arranged, which is formed as a conic gap duct 32 and rotationally symmetric to the longitudinal axis 27 with an annular gap 33. Through this diaphragm aperture 26, a helical purging gas flow 34 indicated by an arrow enters into a dirty atmosphere 35. The purging gas flow 34 expands immediately during the escape from the diaphragm aperture 26 due to the thus generated centrifugal forces in such a manner that no negative pressure can be generated between the purging gas flow 34 and the flank 28 or that the purging gas flow 23 brushes the flank 28. An internal flow guiding device for generating the helical purging gas flow 34 is not illustrated here. The external flow guiding device 31 generates a further purging gas flow 36, which is also indicated with arrows. The purging gas flow 36 leaves the annular gap 33 directly at the outer diameter d in the direction of the longitudinal axis 27 and coincides with the purging gas flow 34. A thus generated negative pressure in the area of the front side 29 causes the formation of a flow 37 indicated by arrows in the dirty atmosphere 35. Dirt particles, which are brought along by the flow 37 and are not illustrated here, are carried away by the purging gas flow 36 before they ever reach the area of the diaphragm aperture 26. Thus, while dirt particles may be deposited at the front side 29, a covering of the diaphragm aperture 26 is not possible because deposited dirt particles cannot pass the annular gap 33 or the purging gas flow 36. Also, a deposition of dirt particles on the flank 28 is largely precluded because no negative pressure is generated here which could promote such a deposition. Thus, dirt particles are carried away from the flank 28 by means of the purging gas flow 34. In this way, the diaphragm aperture 26 can be kept free of dirt.

A combined view of FIGS. 4 to 7 shows a diaphragm device 38 in different illustrations with the diaphragm aperture 26 according to the preceding description of FIG. 3. The diaphragm device 38 serves for protecting an observation opening 39 with a wide angle lens 40 and a camera not illustrated here. Between an optical surface 41 of a protective screen 42 of the observation opening 39 and the diaphragm aperture 26, a purging gas chamber 43 is formed. The purging gas chamber 43 is conic and rotationally symmetric relative to the longitudinal axis 27, tapering towards the opening direction of the diaphragm aperture 26 and formed by an inner diaphragm ring 44. The inner diaphragm ring 44 is screwed together with a support 45 of the protective screen 42 such that between the inner diaphragm ring 44 and the outer diaphragm ring 30, an annular duct 46 is formed. Purging gas made up of nitrogen is supplied at high pressure through a supply duct 47 to the annular duct 46. In the annular duct 46, a rotating purging gas flow indicated by arrows 48 is formed by means not illustrated here.

From the annular duct 46, the purging gas is guided through a flow guiding device 49 illustrated here into the purging gas chamber 43. The internal flow guiding device 49 is formed of a plurality of passage drill holes 50 in the inner diaphragm ring 44, wherein the passage drill holes 50 are arranged with their longitudinal axes 51 in a horizontal direction transverse to the longitudinal axis 27 in such a manner that the longitudinal axes 51 do not intersect the longitudinal axis 27. Thus, with the purging gas flowing through the passage drill holes 50 into the purging gas chamber 43, a twist of the purging gas is created within the purging gas chamber 43, which continues in the purging gas flow 34 when exiting through the diaphragm aperture 26, said twist being indicated by the arrow 52.

The inner diaphragm ring 44 is inserted into the outer diaphragm ring 30 in such a way that between the diaphragm rings 30 and 44, the gap duct 32 with the annular gap 33 is formed. As can be seen in particular from FIG. 4, the gap duct 32 tapers starting from the annular duct 46 in the direction of the diaphragm aperture 26. Thus, the gap duct is formed conic an inclined in the direction of the longitudinal axis 27.

A combined view of FIGS. 8 to 10 shows a nozzle unit 53 of a diaphragm device not illustrated here. The nozzle unit 53 forms a diaphragm aperture 54 formed substantially conic, wherein passage drill holes 55 are arranged such that they exit within a flank 56 of the diaphragm aperture 54. Longitudinal duct axes 57 of the passage drill holes 55 run transverse relative to a longitudinal axis 58 of the diaphragm aperture 54 without intersecting it. Thus, the passage drill holes 55 run parallel and offset to one another by a distance a relative to a longitudinal sectional plane 59 of the nozzle unit 53. Further, the passage drill holes 55 are arranged offset from one another by an angle β.

A combined view of FIGS. 11 and 12 shows a further embodiment of a nozzle unit 60, wherein here, passage drill holes 61 are arranged in the area of a bottleneck 62 between a diaphragm aperture 63 and a purging gas chamber 64 which is only partially illustrated. 

1. A diaphragm device for protecting an optical observation opening, in particular for protecting the observation opening against contaminants from a dirty atmosphere in a blast furnace or the like, said diaphragm device comprising: nozzle unit forming a diaphragm aperture for an observation opening and a purging gas flow; a purging gas chamber formed between an optical surface of the observation opening and the diaphragm aperture, wherein a purging gas is applied to the purging gas chamber; and a flow guiding device forming part of the nozzle unit and guiding the purging gas from the purging gas chamber through the diaphragm and into a dirty atmosphere.
 2. The diaphragm device according to claim 1, in which the purging gas chamber is conical, tapering in an opening direction of the diaphragm aperture.
 3. The diaphragm device according to claim 1, in which the diaphragm aperture is conical, widening in an opening direction of the diaphragm aperture.
 4. The diaphragm device according to claim 1, in which the diaphragm device includes an annular duct through which purging gas can be supplied to the nozzle unit.
 5. The diaphragm device according to claim 1, in which the flow guiding device is rotationally symmetric relative to a longitudinal axis of the diaphragm aperture.
 6. The diaphragm device according to claim 1, in which the nozzle unit includes an internal flow guiding device inducing a helical motion of the purging gas around a longitudinal axis of the diaphragm aperture.
 7. The diaphragm device according to claim 6, in which the internal flow guiding device is arranged between an annular duct and the purging gas chamber.
 8. The diaphragm device according to claim 6, in which the internal flow guiding device is arranged between an annular duct and the diaphragm aperture.
 9. The diaphragm device according to claim 6, in which the internal flow guiding device is arranged between an annular duct and a transition area between the purging gas chamber and the diaphragm aperture.
 10. The diaphragm device according to claim 6, in which the internal flow guiding device forms flow ducts whose longitudinal duct axes run transverse relative to a longitudinal axis of the diaphragm aperture, respectively, without intersecting the longitudinal axis.
 11. The diaphragm device according to claim 10, in which the flow ducts are formed of drill holes or lamellas.
 12. The diaphragm device according to claim 1, in which the nozzle unit comprises an external flow guiding device forming an annular gap surrounding the diaphragm aperture from which purging gas can escape in the shape of a ring.
 13. The diaphragm device according to claim 12, in which the annular gap is formed between an inner and an outer diaphragm ring of the nozzle unit.
 14. The diaphragm device according to claim 12, in which the annular gap is directly connected to an annular duct.
 15. The diaphragm device according to claim 12, in which the annular gap is conical, tapering in the opening direction of the diaphragm aperture.
 16. The diaphragm device according to claim 12, in which a gap duct of the annular gap is formed tapering in an opening direction of the diaphragm aperture.
 17. The diaphragm device according to claim 12, in which the annular gap is arranged directly on an outer diameter (d) of the diaphragm aperture.
 18. A method for protecting an optical observation opening, in particular for protecting the observation opening against contaminants from a dirty atmosphere in a blast furnace or the like, said method comprising: forming a purging gas flow using a nozzle unit, wherein the nozzle unit forms a diaphragm aperture for an observation opening; applying the purging gas to a purging gas chamber between an optical surface) of the observation opening and the diaphragm aperture; and guiding the purging gas from the purging gas chamber into a dirty atmosphere using a flow guiding device forming part of the nozzle unit. 